A transmission system of a machine contains a gear box configured to reduce a rotating speed of a motor to a set value, thus obtaining a large output torque. Taking a worm spindle gearbox for example, it contains at least one gear and a worm spindle meshing with the at least one gear, so the machine has high torque, high reduction ratio, and is manufactured easily, but abrasion, backlash, and poor positioning accuracy occur.
To overcome above-mentioned problems, a conventional roller drive is disclosed in U.S. Pat. No. 7,793,567 and contains a rolling column configured on an outer periphery of a rotary disc and contains a worm spindle meshing with the rolling column. The worm spindle meshes with the rolling column linearly, so high torque, high reduction ratio, low abrasion, zero backlash, and excellent positioning accuracy occur to the machine. However, this roller drive is manufactured at expensive cost, because an accuracy of spaced angle (indexing difference) of the fixing groove of the rolling column is required so as to drive a smooth rotation of the rotary disc.
A conventional ball drive is disclosed in U.S. Pat. No. 8,549,947 and contains plural rolling balls for replacing the rolling column. Nevertheless, the ball drive is assembled difficultly, since the plural rolling balls are fixed in a plurality of accommodating grooves of the rotary disc and roll in plural trenches of the worm spindle smoothly. Accordingly, machining accuracy (such as 1 μm) of each accommodating groove is required, thus increasing machining cost and difficulty.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.